I could easily see myself in this situation. With the exception that I am still in decent shape, and young compared to many on this site. Yes some times I go without my carry weapon due to the place I am going to.
That said I would have had my cell phone in my hand with 911 dialed, and ready to call with hitting the send button before I approached the situation. If I had had my carry weapon with me then my fingers would have been on the grip of my pocket gun ready to draw.
The part about the near falling with the weak knees. I have bad knees from multiple injuries to both. Also after a huge dump of adrenaline it not uncommon after the fact to be weak at the knees. Though I agree you should see a doctor for a cardiac stress test, and to find out if you are healthy enough to start doing some type of exercises it helps to keep the mind and body ready.
Glad to hear that it was a false alarm as well. I hope this turns out to be a wake up call for you as well. I am glad to see that there are still people in this world that are willing to be of help if they can.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.